Vol. 68.] IN THE ' PEEMIAN ' ROCKS OF HAMSTEAD. 



661 



Eothliegende of Thuringia, and also from the Eothliegende of 

 Silesia, Bohemia, and Moravia. The description of the Hamstead 

 type Hj, given on p. 659, will answer equally well for that of the 

 German species. 



Comparative measurements of the English and Continental ex- 

 amples have been tabulated above. Except as regards the smaller 

 average size of the Hamstead specimens, it will be noticed that the 

 two series of measurements agree very closely. Owing possibly 

 to the greater average hardness of the ground on which the Ham- 

 stead species trod at the time of the making of the impressions, 



Fig. 11. — Hamstead form of Ich- 

 nium sphserodactylum (half 

 of the natural size). 



Fig. 12. — Ichnium sphserodacty- 

 lum from Tamhaeh (half of 

 the natural size). 





the first toe of each foot has left a smaller impression than in the 

 German forms, and thus the measurements of our H^ are relatively 

 slightly the smaller. Besides this, the only difference between 

 the Hamstead and German forms is in the breadth of the hind foot, 

 which is proportionately the larger in the Hamstead specimens. 

 As this measurement is determined by taking the distance apart 

 of the tips of the outstretched toes on the inside and outside of the 

 foot, and as a number of the Hamstead specimens have their toes 

 widely stretched, this latter fact may account for the difference. 



Footprints allied to the Hamstead form H^, but not identical 

 with it, are recorded from the Carboniferous rocks of America. 

 These are named Baroj)us lentus and Themaropus heterodactylus. 



Bar opus lentus Marsh, ^ from the Coal Measures of Kansas, 

 shows a certain resemblance to the Hamstead form H^. But that 



^ O. 0. Marsh, * Footprints of Vertebrates in the Coal Measures of Kansas ' 

 Amer. Journ. Sci. ser. 3, vol. xlviii (1894) pp. 81-84, & Geol. Mag. dec 4 

 vol. i (1894) pp. 337-39. ' ' 



